Waters 2475, Operator'S Manual, Page: 177 / 228

User-selected diagnostic tests and settings 5-19
3. Press Enter.
4. In the list of filters, press a number to the corresponding filter, or leave
the default filter (Automatic) on.
5. Press DIAG, and then press 1, or select Automatic for the default filter.
Reducing PMT sensitivity
The detector’s design increases the limit of detection, but in some
circumstances the photomultiplier tube can be overloaded by large
fluorescence signals. You can reduce the sensitivity of the photomultiplier
tube by a constant factor while preserving the available linear gain range of 1
to 1000. This feature is intended for use when samples or mobile phase
solvents exhibit high fluorescence emissions that saturate the PMT signal but
reducing concentration is not possible. The PMT sensitivity is divided by a
user selectable factor of 10 or 100.
Unlike the ordinary PMT gain range of 1 to 1000, the reduction in PMT
sensitivity is not linear, and this function should not be used as a substitute
for ordinary gain changes.
To reduce PMT sensitivity:
1. Press DIAG, and then press 8 Other diagnostics.
2. Press 3 PMT Sensitivity override to reduce the sensitivity by a specified
factor. The PMT Sensitivity screen appears.
Automatic 1
Second Order 2
None 3
Erbium 4
Shutter 5